A rapid development is currently occurring in the field of solar energy. The technological development encompasses a multitude of different areas within the field of solar energy, from simple flat thermal solar collectors for water heating in swimming pools to advanced solar cell systems that by concentrating the sunlight by a thousand times converts sunlight to electricity with an efficiency of over 30%.
In concentrating solar energy systems sunlight is focussed using different optical systems such as reflectors or lenses onto a receiver, in which the concentrated sunlight is converted into other forms of energy, for instance electricity or heat.
One type of concentrating solar energy systems is parabolic troughs where the sunlight is concentrated into a longitudinal line. An example is the 84 m long and 6 m wide Euclides at ITER on Tenerife, that converts sunlight to electricity, and the “Parabolrinnen” by the German company Solar Millennium AG, that heats oil to 400° C.
A concentrating solar energy system comprises a number of components, optical components for concentrating the light, components for continuously tracking the sun, receivers for receiving the concentrated solar radiation, and different kinds of ancillary equipment, such as turbines or hot water heaters.
A particular type of receiver is provided with solar cells in order to allow combined production of electricity and heat. The technology is termed PV/T (photovoltaic/thermal) and examples can be found under the trademark
“Double Solar” from Absolicon Solar Concentrator AB and from the companies Menova and Heliodynamics.
A problem with receivers for combined production of electricity and heat is the combination of high production of electricity and high production of heat. Traditionally, it has been attempted to reduce heat losses by insulating the receiver.
One example of a traditional PV/T receiver is disclosed in U.S. Pat. No. 4,491,681. The receiver is filled with insulating material in order to keep heat losses low.
In solar energy systems possible solutions must be very cost effective in order to allow solar power to compete with other sources of energy.
Hence, there is a need for providing a receiver which is simple and inexpensive to manufacture, in spite of having both solar cells and a high exchange of heat.